1. A large file cutting test is realized by using slice and fileReader. The idea is to segment the files [0] file obtained in the onchange of input type= "file" using files [0] .slice (start,end) according to the size of chunkSize, and instantiate a FileReader object each time in the process of segmentation, listen for onLoad events, and get the corresponding result, result error report after onLoad.
2.`
< html >
< head >
<title>This is a test about file</title> < / head >
< body >
<input type="file" id="myfile" name="myfile" onchange="dealup()"/>
<button onclick="showresult()">Show result</button> < / body >
< script >
const chunkSize = 10;
var myresult = new Array();
function dealup() {
var file =document.getElementById("myfile").files[0];
var chunks = Math.ceil(file.size/chunkSize);
var filder = new Array(chunks);
var start = 0,end = 0;
console.log(""+file.size);
for(let curindex = 0; curindex < chunks;curindexPP) {
var tempcell = {
data: "",
n: 0
};
if(file.size-start <= chunkSize) {
end = file.size;
}else {
end = start + chunkSize;
}
console.log(":"+start + " " + end);
tempcell.n = curindex;
filder[curindex] = new FileReader();
filder[curindex].readAsText(file.slice(start,end));
filder[curindex].onload = function() {
console.log(curindex + "-sharp ")
tempcell.data = filder[curindex].result;
myresult.push(tempcell)
}
start = end;
curindexPP;
}
}
function showresult() {
console.log(myresult);
} < / script >
< / html > `
3. Result:
